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Flow and turbulence characterization as an onset for assessing the stability of gravel beds
Duma, Diana; Erpicum, Sébastien; Archambeau, Pierre et al.
2014In 7th International Conference on Fluvial Hydraulics
Peer reviewed
 

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Keywords :
velocity profile; turbulent kinetic energy; shear velocity; coarse sediments; inception of motion
Abstract :
[en] The flow characteristics, such as velocity profiles and turbulence intensities, are of high practical relevance in the assessment of riverbed stability. So far, the Shields diagram remains the most widely accepted approach for defining the initiation of sediment motion. However, it faces a number of shortcomings. In principle, it is only valid for uniform flow conditions and, under non-uniform flow conditions, it fails to account properly for the influence of turbulence in sediment entrainment. In this paper, we focus on a more detailed description of quasi-uniform and non-uniform flow characteristics in the vicinity of the critical flow conditions for inception of motion of gravel beds. Laboratory experiments were designed, involving two configurations. First, the entire bottom of the flume was paved with stones of uniform diameter (8 or 15 mm), leading to quasi-uniform flow conditions. Second, the flume bottom was smooth upstream of the zone of measurement while the downstream part was covered with gravels, leading to a sudden smooth-to-rough transition. The flow velocity was obtained by acoustic measurements and the turbulence intensity was calculated for both configurations. By fitting the velocity profile to a modified logarithmic law, the shear velocity was estimated. Standard approaches for predicting the threshold of motion, initially developed for uniform flows, were compared to other methods, based on depth-averaged turbulence kinetic energy, recently proposed in literature for non-uniform flow conditions.
Disciplines :
Civil engineering
Author, co-author :
Duma, Diana ;  Université de Liège - ULiège > Département ArGEnCo > Hydraulics in Environmental and Civil Engineering
Erpicum, Sébastien  ;  Université de Liège - ULiège > Scientifiques attachés au Doyen (Sc.appliquées)
Archambeau, Pierre  ;  Université de Liège - ULiège > Département ArGEnCo > HECE (Hydraulics in Environnemental and Civil Engineering)
Pirotton, Michel ;  Université de Liège - ULiège > Département ArGEnCo > HECE (Hydraulics in Environnemental and Civil Engineering)
Dewals, Benjamin  ;  Université de Liège - ULiège > Département ArGEnCo > Hydraulics in Environmental and Civil Engineering
Language :
English
Title :
Flow and turbulence characterization as an onset for assessing the stability of gravel beds
Publication date :
September 2014
Event name :
River Flow 2014
Event organizer :
IAHR
Event place :
Lausanne, Switzerland
Event date :
September 3-5
Audience :
International
Main work title :
7th International Conference on Fluvial Hydraulics
Peer reviewed :
Peer reviewed
Available on ORBi :
since 27 February 2014

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